In the 4th generation (4G) Long-Term-Evolution (LTE) wireless communication systems, to utilize multi-carrier transmission, user equipments (UEs) need to establish a connection to a primary cell (PCell) first, perform measurements in response to the received measurement configurations from the PCell, and send corresponding measurement reports to the current serving base station to determine one or more component carriers (CCs) (e.g., secondary cells (SCells)) to connect to. In the next generation (e.g., the 5th generation (5G) New Radio (NR)) wireless communication networks, multi-carrier transmissions, such as carrier aggregation (CA) and dual connectivity (DC), will operate in higher frequency bands. As such, multi-carrier transmission in the next generation wireless communication networks may need to compensate for the high pathloss in high frequency bands.
Beam operations in high frequency bands, such as high modulation (e.g., 64QAM), need to be supported by high quality signals. Thus, the next generation wireless communication networks need to utilize beamforming gain obtained from directional phase array antennas to enhance data rates. Beamforming gain may be obtained on both transmission (TX) and reception (RX) antennas. While beamforming gain can alleviate performance degradation caused by pathloss, beamforming may result in reduced beam width. Thus, the network and UEs have to perform extra procedures to align beams toward target directions for both TX and RX beamforming to maintain high data rate.
The conventional beam alignment procedure can cause excessive power consumption and severe latency since a UE needs to perform RX beam sweeping to each TX beam from a base station until the UE finds a pair of RX and TX beams, which satisfies a received power requirement. In a case of carrier aggregation of a cell group, a secondary cell (SCell)'s activation and deactivation may happen frequently. It would be unacceptable and/or undesirable if a time-consuming beam alignment procedure needs to be performed for each SCell activation. In addition, for primary SCell (PSCell) addition in dual connectivity, since the dedicate RACH configurations may be provided based on the beam information from the master node, a fast beam alignment procedure for PSCell addition may also be desirable.
Thus, there is a need in the art for an improved beam alignment procedure for both SCell activation and PSCell addition for transmission in multiple component carriers in the next generation (e.g., 5G NR) wireless communication systems.